If an equation won't factorise (the solutions might be decimals or fractions) then you can try the formula. It looks really complicated but once you've practised using it, it will seem much easier (honest!). Anyway, it's based on the form: ax2 + bx + c = 0, and here it is:

You just substitute the numbers in and hey presto! One solution comes from using the + sign in front of the square root and the other solution by using the - sign.

Here's an example:

Solve x2 - 2x - 4 = 0 using the formula.

Here a = 1, b = -2, and c = -4. So we can put these values into the formula: